Tyre for vehicle wheel comprising a particular carcass structure

ABSTRACT

A tire for a vehicle wheel is provided which comprises a carcass structure, and a belt structure applied to the carcass structure at a circumferentially-outer position of the carcass structure. A tread band is also provided which is circumferentially superposed on the belt structure, and sidewalls are laterally applied to opposite sides of the carcass structure. The carcass structure comprises at least one carcass ply, and a pair of annular reinforcing structures, wherein the at least one carcass ply comprises a first series and a second series of strip segments consecutively arranged along a circumferential development of the carcass structure, and each strip segment extends according to a substantially U-shaped conformation. In addition, each strip segment comprises at least two filiform elements, positioned longitudinally and parallel to each other, and at least partially coated by at least one layer of elastomer material. Also, each annular reinforcing structure is engaged in proximity to a respective inner circumferential edge of the at least one carcass ply. Each annular reinforcing structure comprises at least one primary portion, and at least one additional portion, wherein the at least one primary portion comprises an axially-inner side oriented toward terminal edges of the first series of strip segments, and the at least one primary portion comprises an axially-outer side oriented toward terminal edges of the second series of strip segments. Further, the at least one primary portion comprises a first circumferentially-inextensible annular insert, a filling body, and at least one second circumferentially-inextensible annular insert, wherein the first annular insert is substantially annulus-shaped, is positioned coaxially to the carcass structure, adjacent to the respective inner circumferential edge of the at least one carcass ply, and is formed by at least one elongated element extending in concentric turns. Moreover, the filling body is made of elastomeric material, and is joined to the first annular insert. The at least one second annular insert is substantially annulus-shaped, and is positioned coaxially to the carcass structure, axially side-by-side to the filling body and laterally opposite relative to the first annular insert, wherein the at least one second annular insert is formed by at least one elongated element extending in concentric turns, the at least one additional portion is positioned against the terminal edges of the second series of strip segments on a side opposite to the at least one primary portion, the at least one additional portion comprises at least one third circumferentially-inextensible annular insert, the at least one third annular insert is substantially annulus-shaped, the at least one third annular insert is positioned coaxially to the carcass structure, adjacent to the respective inner circumferential edge of the at least one carcass ply, and the at least one third annular insert is formed by at least one elongated element extending in concentric turns,

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/937,601, filed Sep. 28, 2001, which is a national stage entry under35 U.S.C. § 371 from International Application No. PCT/EP0100644, filedJan. 22, 2001, in the European Patent Office; additionally, Applicantclaims the right of priority under 35 U.S.C. § 119(a)-(d) based onpatent application No. 00830058.4, filed Jan. 28, 2002, in the EuropeanPatent Office; further, Applicant claims the benefit under 35 U.S.C. §119(e) based on prior-filed, copending provisional application No.60/190,526, filed Mar. 20, 2000, in the U.S. Patent and TrademarkOffice; the contents of all of which are relied upon and incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a carcass structure for tyres forvehicle wheels, comprising at least a carcass ply having a first and asecond series of strip-like segments consecutively arranged along thecircumferential development of the carcass structure, each of said whichextends according to a substantially “U” shaped conformation andcomprises at least two filiform elements positioned longitudinally andparallel to each other and at least partially coated by at least a layerof raw elastomeric material, and a pair of annular reinforcingstructures each engaged in proximity to a respective interiorcircumferential edge of the carcass ply.

2. Description of the Related Art

The manufacture of tyres for vehicle wheels entails the formation of acarcass structure essentially composed by one or more carcass pliesshaped according to a substantially toroidal configuration andpresenting their axially opposite lateral edges engaged to respectivecircumferentially inextensible annular reinforcing elements, usuallycalled “bead rings”.

On the carcass structure is applied, in circumferentially exteriorposition, a belt structure comprising one or more belt strips shaped asa closed loop, essentially composed by textile or metallic cordssuitably oriented relative to each other and to the cords belonging tothe adjacent carcass plies.

In a position circumferentially exterior to the belt structure, a treadband is then applied, normally constituted by a strip of elastomericmaterial of suitable thickness.

It should be specified that, for the purposes of the presentdescription, the term “elastomeric material” means the rubber compoundin its entirety, i.e. the set formed by at least a polymeric basesuitably amalgamated with reinforcing fillers and/or process additivesof various kinds.

Lastly, on the opposite sides of the tyre being manufactured, a pair ofsidewalls is applied, each of which covers a lateral portion of the tyrelying between a so-called shoulder area, located in proximity to thecorresponding lateral edge of the tread band, and a so-called beadlocated in correspondence with the corresponding bead ring.

Traditional manufacturing methods essentially provide for the tyrecomponents listed above to be first produced separately from each other,then assembled in a tyre manufacturing phase.

For instance, the manufacture of the carcass ply or plies to beassociated to the bead rings to form the carcass structure requiresfirst that, through an extrusion and/or calendering process, arubberised fabric be produced comprising continuous textile or metalliccords, arranged longitudinally. This rubberised fabric is subjected to atransverse cutting operation to produce segments of predetermineddimensions, which are subsequently united to originate a continuousbelt-like semi-finished product, having transversely positioned parallelcords.

This manufactured item must then be cut into segments of a lengthcorrelated to the circumferential development of the carcass to beproduced.

Manufacturing methods have also been proposed which, instead ofproducing semi-finished products, produce the carcass structure directlyduring the tyre manufacturing phase.

For instance, U.S. Pat. No. 5,453,140 describes a method and anapparatus that form a carcass ply starting from a single cord previouslywound on a reel.

According to the method and the apparatus described in this patent, ateach operative cycle of the apparatus the cord drawn from the reel bymeans of motorised driving rollers and kept tensioned by means of apneumatic tensioning system is cut to measure to obtain a segment ofpredefined length.

The cord segment is drawn by a gripping element mounted on a belt woundon motorised pulleys to be laid transversely onto the exterior surfaceof a toroidal support.

The ends of the segment are then engaged by belt folding organsoperating on opposite sides of the toroidal support to apply the cordsegment radially onto the toroidal support itself by means of cursorelements which act in the manner of fingers along the lateral portionsof the segment.

The repetition of the operative cycle described above leads to thelaying of many cord segments in circumferential side by siderelationship until the entire circumferential development of thetoroidal support is involved.

Of necessity, the toroidal support is previously coated with a layer ofraw rubber which has a dual function of adhering to the cords laidthereon in order adequately to hold them according to a fixedpositioning, and of constituting an interior coating, impermeable toair, in the finished tyre.

Tyres obtained through this manufacturing method present a carcassstructure wherein the carcass ply or plies are constituted by singlecords each presenting two lateral portions axially distanced from eachother and oriented radially to the axis of rotation of the tyre, and acrown portion extending in radially exterior position between thelateral portions.

Within the scope of the manufacture of the carcass structure, it is alsoknown that in proximity to each of the beads of the tyre, the oppositeends of the single cords constituting a carcass ply are located, withalternating sequence, in axially opposite positions relative to anannular anchoring element constituting the aforesaid bead ring, shapedin the manner of an annulus composed by wire turns radially superposedon one another, as can be observed from the Patent EP 0 664231 and fromU.S. Pat. 5,702,548.

The cords that compose the carcass ply or plies, however, are positionedsubstantially according to the neutral axis of bending resistance of therespective bead. In this circumstance, the structural strength of thebeads must necessarily be entrusted to the rigidity of filling insertsmade of very hard elastomeric material incorporated in the structure ofthe bead, whose behaviour is affected by temperature variations due bothto environmental factors, and to the stresses induced during normaloperation.

In Patent FR 384 231, the production is proposed of a carcass structureby the laying, onto a toroidal support, of a series of rectangular bandsmade of rubberised fabric circumferentially positioned side by side oneafter the other and arranged according to radial planes relative to thegeometric axis of the supporting drum itself. The laying of the bands isconducted in such a way that the terminal edges of two non-consecutivebands are partially covered by the terminal edges of the band interposedbetween them.

The spaces existing between the terminal edges covered by the bands arefilled by means of trapezoidal inserts applied to the terminal edges ofthe band superposed thereon. The laying of the bands is effectedaccording to several superposed layers, in a number correlated to thethickness to be conferred to the carcass structure. The presence of theaforesaid trapezoidal inserts determines a thickening of the carcassstructure in the areas of the beads, providing it with double thethickness measurable in the rim.

U.S. Pat. No. 4,248,287 describes a method according to which theformation of the carcass structures provides for the laying, on atoroidal drum, of a plurality of layers each formed by radial stripscomposed by rubberised wires and set circumferentially side by siderelative to each other. Once the laying is complete, two bead rings areapplied in the bead area, around which bead rings are then folded backthe terminal edges of the carcass layers formed by the radial strips.

SUMMARY OF THE INVENTION

In accordance with the present invention, it was found that within thescope of the manufacture of a tyre surprising advantages can be obtainedif the carcass ply or plies are produced by laying at least two distinctseries of strip-like segments and providing, in each of the annularstructures reinforcing the beads, two annular inserts that grip theterminal edges belonging respectively to the segments of one of saidseries.

More specifically the invention relates to a carcass structure for tyrescharacterised in that each of said annular reinforcing structurescomprises at least a primary portion presenting an axially interior sideoriented towards terminal edges of the segments belonging to the firstseries and an axially exterior side oriented towards terminal edges ofthe segments belonging to the second series, and at least an additionalportion positioned against the terminal edges of the strip-like segmentsbelonging to the second series, to the opposite side relative to theprimary portion of the annular structure itself; wherein said primaryportion comprises a first circumferentially inextensible annular insertshaped substantially in the manner of an annulus positioned coaxially tothe carcass structure and adjacently to an interior circumferential edgeof the carcass ply, said first annular insert being formed by at leastan elongated element extending according to concentric turns; a fillingbody made of elastomeric material presenting a side joined to the firstannular anchoring insert; at least a second circumferentiallyinextensible annular insert substantially shaped in the manner of anannulus, formed by at least an elongated element extending according toconcentric turns and positioned coaxially to the carcass structure in aposition set axially side by side to the filling body and laterallyopposite relative to the first annular insert; and wherein saidadditional portion comprises at least a third circumferentiallyinextensible annular insert shaped substantially in the manner of anannulus, formed by at least an elongated element extending according toconcentric turns and positioned coaxially to the carcass structure andadjacently to an interior circumferential edge of the carcass ply.

Preferably, said first and second series of strip-like segments arepositioned in a mutually alternated sequence along the entirecircumferential development of the carcass structure.

It is also preferably provided for each of said strip-like segments topresent two lateral portions developing substantially towards ageometric axis of said carcass structure in positions that are mutuallydistanced in the axial direction, and a crown portion extending in aradially exterior position between the lateral portions; the crownportions belonging respectively to the segments of the first and secondseries being set mutually side by side along the circumferentialdevelopment of the carcass structure.

Preferably, the third and second annular inserts present each a lesserradial extension than the radial extension of the first annular insert.More specifically, the third circumferentially inextensible annularinsert presents a lesser radial extension, measuring between ⅓ and ⅔ ofthe radial extension of the first circumferentially inextensible annularinsert.

It may also be provided for the second circumferentially inextensibleannular insert to present a lesser radial extension measuring between ⅓and ⅔ of the radial extension of the first circumferentiallyinextensible annular insert.

Preferably, said carcass structure further comprises an auxiliaryfilling body made of elastomeric material, situated in an axiallyexterior position against said at least one carcass ply and extending inradial separation from said third annular insert.

Said auxiliary filling body preferably presents a hardness substantiallyequal to that of the filling body belonging to the primary portion.

The invention further relates to a tyre comprising a carcass structurepresenting one or more of the particular features described.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages shall become more readily apparent fromthe detailed description of a preferred, but not exclusive, embodimentof a carcass structure for tyres for vehicle wheels, according to thepresent invention. The description shall be made below with reference tothe accompanying drawings, provided purely by way of non limitingindication, in which:

FIG. 1 is an interrupted and cut out view of a tyre provided with acarcass structure manufactured in accordance with the present invention;

FIG. 2 is a diagram showing the manufacture of a continuous strip-likeelement destined to form the carcass ply or plies;

FIG. 3 shows, in cross section view, an embodiment of the aforesaidstrip-like element;

FIG. 4 shows an interrupted perspective view of a schematicrepresentation of the laying sequence of a first series of strip-likesegments in order to form a carcass ply of the tyre according to theinvention;

FIG. 5 shows an interrupted perspective view of a primary portion of aninextensible annular reinforcing structure applied laterally on terminaledges of the strip-like segments belonging to the first series;

FIG. 6 shows an interrupted perspective view of the carcass structureafter the application of a third annular insert and of an auxiliaryfilling body comprised in an additional portion of the bead reinforcingstructure;

FIG. 7 is a cross section showing a tyre according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the aforementioned figures, the number 1 globallyindicates a tyre for wheels of vehicles, having a carcass structure 2manufactured in accordance with the present invention.

The carcass structure 2 has at least a first carcass ply 3 shapedaccording to a substantially toroidal configuration and engaged, bymeans of its opposite circumferential edges, to a pair of inextensibleannular structures 4 each of which, once the tyre has been completed, islocated in the area usually identified with the name of “bead”.

On the carcass structure 2 is applied, in circumferentially exteriorposition, a belt structure 5 comprising one or more belt strips 6 a, 6 band 7. To the belt structure 5 is circumferentially superposed a treadband 8 whereon, following a moulding operation performed simultaneouslywith the curing of the tyre, longitudinal and/or transverse recesses 8 aare obtained, arranged to define a desired “tread design”.

The tyre further comprises a pair of so-called “sidewalls” 9 appliedlaterally at opposite sides onto the carcass structure 2.

The carcass structure 2 can be coated on its inner walls by a sealinglayer 10 or so-called “liner”, essentially constituted by a layer ofelastomeric material impermeable to air able to guarantee the hermetictightness of the inflated tyre.

The assembly of the components listed above, as well as the manufactureof one or more thereof, takes place with the aid of a toroidal support11, schematically indicated in dashed lines in FIG. 1, shaped accordingto the configuration of the inner walls of the tyre to be manufactured.

The toroidal support 11 can have smaller dimensions than the finishedtyre, according to a linear measurement preferably ranging between 2%and 5%, taken, by way of indication, along the circumferentialdevelopment of the support itself in correspondence with its equatorialplane, which coincides with the equatorial plane of the tyre itself.

The toroidal support 11, neither described nor illustrated in detailbecause it is not particularly relevant for the purposes of theinvention, can for instance be constituted by a collapsible drum or byan inflatable tube suitably reinforced to assume and maintain thedesired toroidal shape in the inflated condition.

All this having been stated, the manufacture of the tyre 1 entails firstthe formation of the carcass structure 2, which starts with the possibleformation of the sealing layer 10.

This sealing layer 10 can advantageously be obtained bycircumferentially winding about the toroidal support 11 at least aribbon-like band 12 made of elastomeric material impermeable to air,produced by a strainer and/or by a calender situated in the vicinity ofthe toroidal support itself. As can be observed from FIG. 1, the windingof the ribbon-like band 12 takes place substantially according tocircumferential turns consecutively set by side to follow the crosssection profile of the outer surface of the toroidal support 11.

For the purposes of the present invention the term cross section profilemeans the configuration presented by the semi-section of the toroidalsupport 11 sectioned according to a plane radial to its own geometricaxis of rotation, not shown in the drawings, coinciding with thegeometric axis of rotation of the tyre and, hence, of the carcassstructure 2 being manufactured.

The carcass ply 3 is formed directly on the toroidal support 11 bylaying, as shall become clearer farther on, a first and a second seriesof strip-like segments 13, 14, obtained from at least a continuousstrip-like element 2 a preferably presenting a width ranging between 3mm and 15 mm.

As FIG. 2 shows, the preparation of the continuous strip-like element 2a essentially provides for one or more filiform elements 15, andpreferably three to ten filiform elements 15, fed by respective reels 15a, to be guided through a first strainer 16 associated to an extrusionapparatus 17 which feeds raw elastomeric material through the straineritself.

It is specified that, for the purposes of the present description, theterm “strainer” means the part of the extrusion apparatus identified inthe art also with the term “extrusion head”, provided with a so-called“die” traversed by the product being processed in correspondence with anexit port shaped and dimensioned according to the geometric anddimensional characteristics to be given to the product itself.

The elastomeric material and the filiform elements 15 are intimatelyunited inside the strainer 16, generating at the output thereof thecontinuous strip-like element 2 a, formed by at least a layer ofelastomeric material 18 in whose thickness are incorporated the filiformelements themselves.

Depending on requirements, it is possible to guide the filiform elements15 into the strainer 16 in such a way that they are not integrallyincorporated into the layer of elastomeric material 19 but emerge fromone or both its surfaces.

The filiform elements 15 can, for instance, be constituted each by atextile cord with a diameter preferably ranging between 0.6 mm and 1.2mm, or by a metal cord, with a diameter preferably ranging between 0.3mm and 2.1 mm.

Advantageously, if required, the filiform elements 15 can be positionedin the continuous strip-like element 2 a in such a way as to provideunexpected characteristics of compactness and homogeneity to the carcassply 3 thereby obtained.

For this purpose, the filiform elements 15 can, for instance, bearranged according to a density exceeding six filiform elements percentimetre, measured circumferentially on the carcass ply 3 in proximityto the equatorial plane of the tyre 1. It is in any case preferablyprovided for the filiform elements 15 to be positioned in the strip-likeelement 2 a according to a distance between their respective centres nosmaller than 1.5 times the diameter of the filiform elements themselves,in order to allow for adequate rubberising between adjacent wires.

The continuous strip-like element 2 a exiting the strainer 16 canadvantageously be guided, possibly through an accumulating-compensatingdevice 17 a, onto a laying apparatus whose structural and operatingcharacteristics are described more in detail in document EP 928680 A, inthe name of the same Applicant, whose content is considered enclosedherein.

This laying apparatus is able sequentially to cut the continuousstrip-like element 2 a to obtain strip-like segments 13, 14 ofpredetermined length.

The execution of the cutting of each strip-like segment 13, 14 isimmediately followed by the laying of the segment onto the toroidalsupport 11, shaping the strip-like segment according to a “U”configuration around the cross section profile of the toroidal supportitself, in such a way that in the strip-like segment 13, 14 can beidentified two lateral portions 19, 20 radially developing towards theaxis of the toroidal support 11, in positions that are axially distancedfrom each other, and a crown portion 21, 22 extending in radiallyexterior position between the lateral portions themselves.

The stickiness of the raw elastomeric material forming the layer 18which coats the filiform elements 15 assures the stable adhesion of thestrip-like segments 13, 14 on the surfaces of the toroidal support 11,also in the absence of the sealing layer 10 on the toroidal supportitself. More in particular, the adhesion described above is manifestedas soon as the strip-like segment 13, 14 comes in contact with thetoroidal support 11 in a radially exterior area of its cross sectionprofile.

In addition or instead of the exploitation of the natural stickiness ofthe elastomeric material, as described above, the holding of one or moreof the strip-like segments 13, 14 on the toroidal support 11 can beobtained by means of an aspirating action produced through one or moresuitable holes provided on the toroidal support itself.

The toroidal support 11 can be actuated in angular rotation according toa stepped motion in synchrony with the actuation of the aforesaid layingapparatus, in such a way that each cutting action on each strip-likesegment 13, 14 is followed by its laying in a circumferentiallydistanced position relative to the previously laid segment 13, 14.

More specifically, the rotation of the toroidal support 11 takes placeaccording to an angular pitch whereto corresponds a circumferentialdisplacement equal to a multiple of, and more precisely to double, thewidth of each strip-like segment 13, 14.

It should be noted that, for the purposes of the present description,unless otherwise indicated, the term “circumferential” refers to acircumference lying in the equatorial plane and in proximity to theexterior surface of the toroidal support 11.

According to the present invention, the operative sequence describedabove is such that a first complete revolution of the toroidal support11 about its own axis determines the laying of the first series ofstrip-like segments 13, circumferentially distributed according to acircumferential pitch equal to twice the width of each of them.Therefore, as FIG. 4 clearly shows, between one and the other of thesegments belonging to the first series an empty space “S” is left which,at least in correspondence with the crown portions 21 of the segmentsthemselves, equals the latter in width.

The manufacture of a carcass structure 2 then proceeds with the phasewhereby the aforementioned inextensible annular structures 4, and morespecifically primary parts 4 a thereof, are applied in proximity to eachof the interior circumferential edges of the carcass ply 3 beingmanufactured, in order to obtain the carcass areas, known as “beads”,especially destined to guarantee the anchoring of the tyre to acorresponding mounting rim.

The primary portion 4 a of each of the aforesaid annular reinforcingstructures 4 comprises a first circumferentially inextensible annularinsert 23, shaped substantially in the manner of a circular crownconcentric to the geometric axis of rotation of the toroidal support 11and located in a circumferentially interior position against terminaledges 19 a presented by the strip-like segments 13 belonging to thefirst series.

The first annular insert 23 is composed by at least a metallic elongatedelement wound according to multiple, substantially concentric, turns 23a. The turns 23 can be defined by a continuous spiral or by concentricrings formed by respective elongated elements.

The first annular insert 23 is combined with a second circumferentiallyinextensible annular insert 24 which extends substantially according toa respective annulus coaxially set side by side relative to the firstannular insert 23 at an appropriate distance therefrom.

The second annular insert 24 is also preferably composed by at least ametallic elongated element wound according to multiple, substantiallyconcentric, turns 24, which can be defined by a continuous spiral or byconcentric loops formed by respective elongated elements.

The second annular insert 24 presents a radial extension, determined bythe difference between the minimum inner radius and the maximum outerradius of the annular insert itself, that is preferably lesser than, andmore specifically ranging between ⅓ and ⅔ of, the radial extension ofthe first annular insert 23.

Between the first and the second annular insert 23, 24 is interposed atleast a filling body 25 made of elastomeric material, preferablythermoplastic, having hardness ranging between 48° and 55° Shore D,measured at a temperature of 23° C.

The manufacture of the first portions 4 a can entail the formation ofthe first filling body 25 separately from the first annular insert 23,and the subsequent union of the first filling body itself with the firstannular insert previously applied against the terminal edges 19 a of thestrip-like segments 13 laid onto the toroidal support 11.

More specifically, in accordance with a preferential embodiment, thefirst annular insert 23 is manufactured directly against the terminaledges 19 a of the strip-like segments 13 by laying at least an elongatedelement according to concentric turns 23 a arranged in mutualside-by-side relationship, according to circumferences withprogressively increasing diameter about their geometric winding axis,corresponding to the axis of rotation of the finished tyre.

The winding of the filiform element can be effected with the possibleaid of rollers or other convenient means acting in contrast with thesurface of the toroidal support 11.

The stickiness of the elastomeric layer 18 that coats the strip-likesegments 13 belonging to the first series, as well as of the possiblesealing layer 10 previously laid on the drum itself, assure the stablepositioning of the individual turns 23 a being formed.

Subsequently, the filling body 25 can in turn be formed directly againstthe annular anchoring insert 23, for instance applying a continuousstrip made of elastomeric material exiting a strainer positionedadjacently to the drum 11. The continuous strip can present the finalsection conformation of the filling body 25, already as it exits therespective strainer. Alternatively, the continuous strip will present asmaller cross section than that of the filling body, and the lattershall be obtained applying the strip itself according to multiple turnsset side by side and/or superposed, to define the filling body 25 in itsfinal configuration.

Subsequently, the second insert 24 may be manufactured directly on thepreviously formed filling body 25 by laying an elongated elementaccording to concentric turns 24 a, in a similar manner to the onedescribed with reference to the first insert 23.

After the application of the primary portions 4 a of the respectiveannular reinforcing structures 4, the formation of the first carcass ply3 is completed by laying the second series of strip-like segments 14obtained by cutting to measure the continuous strip-like element 2 a andapplied on the toroidal support 11 in a manner similar to the onedescribed for the strip-like segments 13 belonging to the first series.

Each segment 14 belonging to the second series is laid according to a“U” conformation around the cross section profile of the toroidalsupport 11, between two consecutive segments 13 belonging to the firstseries. More specifically each segment 14 belonging to the second seriespresents the respective crown portion 22 circumferentially interposedbetween the crown portions 21 of the segments 13 belonging to the firstseries, to fill the space “S” existing between them, and a pair oflateral portions 20 which bring the terminal edges 20 a of the segmentitself in superposition to the respective primary portions 4 a of theannular reinforcement structures 4, in axially opposite positionsrelative to the terminal edges 19 a of the segments 13 belonging to thefirst series.

In other words, the primary portion 4 a of each annular reinforcingstructure 4, having a section profile shaped substantially in the mannerof a triangle with its vertex oriented away from the axis of the tyre,presents an axially interior side oriented towards the terminal edges ofthe strip-like segments 13 belonging to the first series, and an axiallyexterior side oriented towards the terminal edges 20 a of the segments14 belonging to the second series.

The lateral portions 20 of each segment 14 belonging to the secondseries can also partially cover the lateral portions 19 of twoconsecutive segments 13 belonging to the first series, each in a lengthlying between the radially exterior edge 25 a of the respective primaryportion 4 a and the transition area between the lateral portion itselfand the crown portion 21.

The superposition areas of the strip-like segments 13 belonging to thefirst series are indicated as 13 a in FIG. 6.

Due to the mutual convergence between the contiguous lateral portions19, 20, oriented radially to the geometric axis of the toroidal support11, the superposition or covering of the lateral portions 19 of thesegments 13 belonging to the first series, i.e. the circumferentialamplitude of the superposition areas 13 a, progressively diminishesstarting from a maximum value in proximity to the radially exterior edge25 a of the primary portion, 4 a of each annular reinforcing structure4, down to a value of zero in correspondence with the transition areabetween the lateral portions 19, 20 and the crown portions 21, 22.

If, in proximity to the beads, a more homogeneous distribution of thefiliform elements 15 respectively composing the segments 13, 14 of thefirst and of the second series is to be obtained, a deflection step canbe executed sequentially on the continuous strip-like element 2 a in theareas of its longitudinal development corresponding to the extremitiesof the strip-like segments 13, 14 to be obtained following the cuttingactions. In this way, on the development of each strip-like segment 13,14, areas with increased width are defined, positioned in correspondencewith the interior circumferential edges of the carcass ply 3 thusformed.

The deflection action causes a reduction in the thickness of theelastomeric layer 18 and an increase in the width of the strip-likeelement 2 a with the consequent mutual separation of the filiformelements 15. In so doing, the terminal edges 19 a, 20 a of each segment13, 14 can be widened until they present, in correspondence with thecircumferentially interior extremities, a width that is twice that ofthe crown portions 21,22, such as to coat completely the respectiveinterior and exterior sides of the primary portions 4 a of each annularreinforcing structure 4.

After laying the strip-like segments 14 belonging to the second seriesin the manner described above, the formation of the annular beadreinforcing structures 4 is completed.

For this purpose, for each of the reinforcing structures 4 a thirdcircumferentially inextensible annular insert 26 is formed, whichextends substantially according to a respective annulus set coaxiallyside by side relative to the second annular insert 24.

The third annular insert 26, too, is preferably composed by at least ametallic elongated element wound according to multiple, substantiallyconcentric turns 26 a, which can be defined by a continuous spiral or byconcentric loops formed by respective elongated elements. Moreover, thethird annular insert also preferably has a radial extension, determinedby the difference between the minimum inner radius and the maximum outerradius of the annular insert itself, that is lesser than, and preferablyranges between ⅓ and ⅔ of the radial extension of the first annularinsert 23.

The third insert 26 thus constitutes an additional portion of thereinforcing structure 4, which is applied against the terminal edges 20a of the strip-like segments 14 belonging to the second series, forinstance by effecting the winding of the respective elongated elementdirectly against the terminal edges themselves.

Following this operation, each of the terminal edges 20 a of thesegments 14 belonging to the second series is advantageously enclosedbetween the second annular insert 24 and the third annular insert 26.

Also provided is the addition of an auxiliary filling body 27 made ofelastomeric material placed in an axially exterior position against thecarcass ply 3 and extending radially away from said third annular insert26.

Preferably, the hardness of the auxiliary filling body 27 issubstantially equal to the hardness of the filling body 25.

In radial tyres, a belt structure 5 is usually applied to the carcassstructure 2.

This belt structure 5 can be obtained in any manner convenient to theperson versed in the art and, in the illustrated embodiment, essentiallycomprises a first and a second belt strip 6 a, 6 b presenting cords withrespectively crossed orientation. To the belt strips is superposed anauxiliary belt strip 7 for instance obtained by winding at least acontinuous cord according to turns set axially side by side on the firstand second belt strip 6 a, 6 b.

On the belt structure 5 are then applied the tread band 8 and thesidewalls 9, also obtainable in any manner found convenient by theperson versed in the art.

Embodiments of a belt structure, of sidewalls and of a tread band thatcan be advantageously adopted for the complete manufacture of the tyre 1on the toroidal support 11 are described in the document EP 919406 A inthe name of the same Applicant.

The tyre 1 thus manufactured can now be subjected, after its removalfrom the support 11, to a curing phase which can be conducted in anyknown and conventional manner.

The present invention achieves important advantages.

The subject carcass structure can be obtained directly on a toroidalsupport whereon, advantageously, the entire tyre can be formed, withconsiderable reduction in processing times compared to the methoddescribed in document U.S. Pat. No. 5,362,343.

The constructive and structural conception of the subject tyre,especially with reference to its carcass structure 2, allows to achieveconsiderable improvements in terms of structural resistance, especiallyin proximity to the sidewalls and beads, where greater structuralstrength is normally required, as well as behaviour, particularly inrelation to the effects of the drift thrusts that manifest themselvesduring travel in curves, while benefiting from all the advantagestypically connected to a single-ply carcass structure.

In particular, the constructive features of the inextensible annularstructures 4 and the manner whereby they are integrated in the carcassply are such as further to enhance the excellent structural resistanceof the tyre 1 in the areas of the beads and sidewalls.

The presence of the circumferentially inextensible annular inserts 23,24 and 26, are intimately joined to the carcass ply 3, provides anexcellent “bond” with the filiform elements 15 belonging to thedifferent series of strip-like segments. The carcass structure 2 isthereby further strengthened in the areas corresponding to the beads ofthe tyre 1 without requiring, for this purpose, the use of additionalstrip-like inserts, usually called “flippers”, wound in a loop aroundthe annular reinforcing structures 4, used instead in the prior art.

In particular the presence of the second and third annular inserts whichgo to enclose the terminal edges 20 a of the second series of thestrip-like segments 14 brings about a particular strength of the beadwithout requiring an excessive radial development of the annular insertsthemselves relative to the first annular insert. The reduced radialdevelopment of the second and third insert 24, 26 thus allows to obtaina space for the possible insertion of the auxiliary filling body 27which can be provided, for instance to confer a greater strength andself-support capacity to the whole tyre.

The increase in structural strength in correspondence with the sidewallshas advantageously been obtained without entailing an excessivestiffening of the carcass structure in the crown, where the segments ofthe single ply 3 are set circumferentially side by side in the absenceof mutual superposition. This aspect is particularly advantageous withreference to high-performance tyres with lowered profile where thestructure resistance of the sidewalls is a very critical item, also dueto the high torque values the tyre must be able to transmit.

1-8. (canceled)
 9. A tyre for a vehicle wheel, comprising: a carcassstructure; a belt structure applied to the carcass structure at acircumferentially outer position of the carcass structure; a tread bandcircumferentially superposed on the belt structure; and sidewallslaterally applied to opposite sides of the carcass structure; whereinthe carcass structure comprises: at least one carcass ply; and a pair ofannular reinforcing structures; wherein the at least one carcass plycomprises a first series and a second series of strip segmentsconsecutively arranged along a circumferential development of thecarcass structure, wherein each strip segment extends according to asubstantially U-shaped conformation, wherein each strip segmentcomprises at least two filiform elements, positioned longitudinally andparallel to each other, at least partially coated by at least one layerof elastomer material, wherein each annular reinforcing structure isengaged in proximity to a respective inner circumferential edge of theat least one carcass ply, wherein each annular reinforcing structurecomprises: at least one primary portion; and at least one additionalportion; wherein the at least one primary portion comprises an axiallyinner side oriented toward terminal edges of the first series of stripsegments, wherein the at least one primary portion comprises an axiallyouter side oriented toward terminal edges of the second series of stripsegments, wherein the at least one primary portion comprises: a firstcircumferentially inextensible annular insert; a filling body; and atleast one second circumferentially inextensible annular insert; whereinthe first annular insert is substantially annulus-shaped, wherein thefirst annular insert is positioned coaxially to the carcass structure,adjacent to the respective inner circumferential edge of the at leastone carcass ply, wherein the first annular insert is formed by at leastone elongated element extending in concentric turns, wherein the fillingbody is made of elastomeric material, wherein the filling body is joinedto the first annular insert, wherein the at least one second annularinsert is substantially annulus-shaped, wherein the at least one secondannular insert is positioned coaxially to the carcass structure, axiallyside-by-side to the filling body and laterally opposite relative to thefirst annular insert, wherein the at least one second annular insert isformed by at least one elongated element extending in concentric turns,wherein the at least one additional portion is positioned against theterminal edges of the second series of strip segments on a side oppositeto the at least one primary portion, wherein the at least one additionalportion comprises at least one third circumferentially inextensibleannular insert, wherein the at least one third annular insert issubstantially annulus-shaped, wherein the at least one third annularinsert is positioned coaxially to the carcass structure, adjacent to therespective inner circumferential edge of the at least one carcass ply,and wherein the at least one third annular insert is formed by at leastone elongated element extending in concentric turns.
 10. The tyre ofclaim 9, further comprising a sealing layer disposed on an inner wall ofthe carcass structure.
 11. The tyre of claim 9, wherein the at least onesecond annular insert and the at least one third annular insert comprisea lesser radial extension than a radial extension of the first annularinsert.
 12. The tyre of claim 9, wherein the at least one third annularinsert comprises a radial extension greater than or equal to one-thirdand less than or equal to two-thirds of a radial extension of the firstannular insert.
 13. The tyre of claim 9, wherein the at least one secondannular insert comprises a radial extension greater than or equal toone-third and less than or equal to two-thirds of a radial extension ofthe first annular insert.